Engine head gaskets have traditionally served a multitude of functions beyond merely the conventional formation of a seal between the block and head for engine lubrication, coolant and combustion cylinder gases. Such functions tend to be peculiar to the particular engine for which the head gasket is designated. For example, U.S. Pat. No. 2,188,876 to Fahlman discloses the concept of varying the sizing of openings in the head gasket to obtain the desired flow of coolant through specific zones of the engine block and head. In particular, Fahlman discloses a cylinder head for an engine wherein coolant enters the cylinder block at the front end of the engine and exits the engine at a longitudinally central point at one side of the cylinder head, and that is designed for obtaining a substantially uniform temperature around the combustion chambers and an equalized cooling effect. To do so, Fahlman not only takes into account the distance of the passages between the head and block from the coolant inlet, but also takes into account the fact that parts of the engine will have different cooling requirements than other parts. In particular, the head is treated in stages corresponding to respective sides of each of the combustion chambers (5 stages in a 4 cylinder engine) with the coolant flow being proportioned from section to section and within each section.
However, in addition to the complexities of implementing Fahlman's method of cooling an internal combustion engine, the disclosure of this patent fails to take into consideration the fact that a fuel supply system, such as a fuel injector, and a valve arrangement normally are situated in the cylinder head and place practical limitations on the manner in which coolant may be circulated (the engine disclosed in U.S. Pat. No. 2,188,876 having no disclosed fuel supply means or valves associated with its engine cylinders).
U.S. Pat. No. 4,284,037, owned by the assignee of the present application, discloses an internal combustion engine coolant system having coolant feed and collection manifolds provided on one side of the cylinder block adjacent each other, and a coolant pump mounted adjacent to and connected with the manifolds on the block. For each cylinder, separate flow passages are formed on the block which conduct the coolant from the feed manifold around the cylinder, up and into the head, across the head and adjacent the injector and the valves, and then down from the head into the collection manifold on the block.
The respective flow paths of coolant through the head are substantially separated and the sizes of the flow passages associated with the various paths are designed to obtain a uniform heat transfer pattern among the various cylinders by controlling the quantity of flow in each path and by providing a valve orientation wherein, for each cylinder, two valves are on the longitudinal axis of the head and another two are on a line that is perpendicular to this axis. Along with partition walls which prevent the coolant from flowing straight across the head, this arrangement forces the coolant to flow at 45 degree angles between pairs of valves to and from the injector, the coolant flowing above and below the exhaust passages after having passed the injector. Additionally, the exhaust ports are relatively close to the exhaust manifold side of the head and the exhaust passages are relatively short, whereby the heated exhaust is removed from the head as quickly as possible.
However, problems exist in adapting such an engine configuration to engines wherein all of the cylinder valves are arranged in a longitudinally extending line, a single pair of closely spaced valves being provided at each cylinder and the injector being situated at a lateral side of the valves opposite the coolant feed and collection manifolds. For example, the cross paths can no longer be maintained and the laterally positioned injector interferes with cooling of the valves by the flow coming across the head after having come up from the cylinder block, since the injector partially shields same. On the other hand, obtaining of the most compact configuration for the engine (for purposes of minimizng weight and space requirements), as well as other considerations, make it impossible to place the various parts so as to facilitate coolant distribution. Certainly, no one has suggested a head gasket design which overcomes the problems associated with obtaining optimum coolant flow in engines having a single pair of valves and a fuel injection or described above.